Power generation system

Abstract

To provide a power generation system capable of reducing man-hours and costs for making it possible to connect a power generation unit comprising an inverter different from system interconnection technical requirements of a power system of a connection destination, to the power system.SOLUTION: A power generation system (1) to be connected to a power system (30) comprises: a power generation unit (10) including an inverter (13) for converting primary side DC power to primary side AC power and outputting the primary side AC power, the inverter (13) not meeting system interconnection technical requirements of the connection destination power system (30); an AC / DC converter (21) for converting the primary side AC power output from the power generation unit (10) to secondary side DC power and outputting the secondary side DC power; a DC / AC converter (23) that meets the system interconnection technical requirements of the connection destination power system (30) and converts the secondary side DC power output from the AC / DC converter (21) to secondary side AC power and outputs the secondary side AC power; and a controller (40) for controlling the power generation system (1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power generation system connected to a power grid. [Background technology]

[0002] In recent years, a system has been established in which electricity generated by power generation units installed in ordinary households, businesses, etc. is sold to electricity transmission and distribution companies. In order to supply the electricity generated by power generation units installed in ordinary households, businesses, etc. to the power grid of the electricity transmission and distribution company, the power generation units are required to satisfy grid interconnection technical requirements. The grid interconnection technical requirements include various requirements, such as electrical system requirements (number of AC phases and number of power lines), operating frequency requirements for the power generation device, power factor requirements, power generation output requirements, and voltage fluctuation requirements. To meet these grid interconnection technical requirements, the power generation units are equipped with an inverter to satisfy the grid interconnection technical requirements. The inverter consists of, for example, an inverter circuit that converts the generated DC power into AC power that satisfies the grid interconnection technical requirements. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-013275 Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that grid interconnection technical requirements vary from country to country or region to region due to, for example, differences in the system voltage or frequency of the power system. Therefore, in order to connect a power generation unit equipped with an inverter that does not meet the grid interconnection technical requirements of the connected power system to a grid, it is necessary to modify the inverter, replace the inverter with one that meets the grid interconnection technical requirements, or add an external protection device between the inverter and the power system. For example, in order to connect a power generation unit manufactured to the specifications of a country different from the country in which the power generation unit is used to the power system of that country, it is necessary to modify or replace the inverter or add a protection device to meet the specifications of the country in which the power generation unit is used.

[0005] However, in some cases, the inverter is integrated into the power generation unit, which is not practical because the inverter manufacturer must modify the inverter. Furthermore, replacing the inverter requires redesigning the control system between the power generation system and the inverter, which can require a great deal of effort and cost.

[0006] 4 is a reference diagram showing an example of a configuration for connecting a power generation unit 60 configured with an inverter 63 that does not satisfy the grid interconnection technical requirements to a power grid 70. The power generation unit 60 includes a power generation device 61 such as a fuel cell or a solar cell, an inverter 63 that converts DC power generated by the power generation device 61 into AC power of a predetermined voltage value and frequency, and auxiliary equipment 65 used to drive the power generation device 61.

[0007] If the inverter 63 does not satisfy the grid interconnection technical requirements of the power grid 70 and it is difficult to modify or replace only the inverter 63 of the power generating unit 60, it is necessary to connect the transformer 51 and the protective device 53 to the outside of the power generating unit 60 in order to adjust the voltage value of the AC power output from the power generating unit 60 to the grid voltage value of the power grid 70. Furthermore, if the rated voltage value of the external power supply used for the auxiliary equipment 65 is different from the grid voltage value of the power grid 70, it is also necessary to connect the auxiliary equipment 65 to the power grid 70 via the transformer 55 or the like. However, attaching the protective device 53 externally may require a great deal of man-hours and cost for selecting and designing the protective device 53, and it is also necessary to conduct a new field test or the like to confirm its operation.

[0008] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a power generation system that can reduce the labor and cost required to connect to a power system a power generation unit equipped with an inverter configured to specifications that do not satisfy the grid interconnection technical requirements of the power system to which it is connected. [Means for solving the problem]

[0009] In order to solve the above problem, according to one aspect of the present invention, there is provided a power generation system that is connected to a power grid, the power generation system comprising: a power generation unit including an inverter that converts primary side DC power into primary side AC power and outputs the inverter, the inverter being configured to specifications that do not satisfy the grid interconnection technical requirements of the connected power grid; an AC / DC converter that converts the primary side AC power output from the power generation unit into secondary side DC power and outputs the secondary side DC power; a DC / AC converter that is configured to specifications that satisfy the grid connection technical requirements of the connected power grid, and that converts the secondary side DC power output from the AC / DC converter into secondary side AC power and outputs the secondary side DC power; and a control device that controls the power generation system. [Effects of the Invention]

[0010] As described above, according to the present invention, it is possible to reduce the labor and costs required to connect a power generation system equipped with an inverter configured to specifications that do not satisfy the grid interconnection technical requirements of the power grid to which it is connected to a power grid. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram showing a configuration example of a power generation system according to a first embodiment of the present invention. [Figure 2] FIG. 4 is an explanatory diagram showing a configuration example of a power generation system according to a second embodiment of the present invention. [Figure 3] FIG. 2 is an explanatory diagram showing the power conversion efficiency of the power generation system. [Figure 4] FIG. 1 is an explanatory diagram showing a configuration example of a conventional power generation system. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant explanations will be omitted.

[0013] First Embodiment An example of the configuration of a power generation system 1 according to a first embodiment will be described with reference to FIG. 1 is a schematic diagram showing the overall configuration of a power generation system 1. The power generation system 1 includes a power generation unit 10, an AC / DC converter 21, a DC / AC converter 23, an auxiliary DC / AC converter 25, and a control device 40, and is connected to an electric power grid 30.

[0014] The power grid 30 is constructed by, for example, a power transmission and distribution company, and is a power system that integrates power generation, power transformation, power transmission, and power distribution. The power grid 30 generates, transforms, transmits, and distributes power, each at a predetermined voltage value. The system voltage value of the power grid 30 is determined for each country or region. The frequency of the power used in the power grid 30 is also determined for each country or region. Grid interconnection technical requirements are determined for the power grid 30 in order to receive a stable and safe supply of power from the power generation system 1.

[0015] In this embodiment, an example will be described in which a power generation unit 10 is configured to specifications that satisfy the grid interconnection technical requirements and legal standards of a first country, and the power generation unit 10 is connected to a power grid 30 of a second country that has different grid interconnection technical requirements and legal standards. However, differences in the specifications of the power generation unit 10 and the power grid 30 are not limited to differences between countries, but may also be differences between regions within the same country.

[0016] The power generation unit 10 includes a power generation device 11, an inverter 13, and auxiliary machinery 15. The power generation device 11 is a device with a power generation function, such as a fuel cell or a solar cell. The power generation device 11 is not limited to a fuel cell or a solar cell, but may be other power generation devices such as a wind power generation device or a hydroelectric power generation device. The fuel cell may also be a fuel cell system mounted on a vehicle. Furthermore, the power generation device 11 may be a power storage device that stores power and can discharge the stored power. In this embodiment, an example will be described in which the power generation device 11 is a fuel cell.

[0017] A fuel cell is a device that generates electricity by causing an electrochemical reaction between supplied fuel gas and oxidizing gas. A fuel cell is configured as a fuel cell stack made up of multiple stacked cell structures. For example, hydrogen gas is used as the fuel gas, and air is used as the oxidizing gas. The auxiliary equipment 15 of the power generation unit 10 includes a fuel gas supply system and an oxidizing gas supply system driven by a control device 40. The fuel gas supply system includes one or more solenoid valves and supplies hydrogen gas from a hydrogen supply source such as a hydrogen gas tank to the fuel cell stack. The oxidizing gas supply system includes a compressor and one or more solenoid valves and pressurizes air to the fuel cell stack. The control device 40 controls the supply flow rate and supply pressure of the fuel gas and oxidizing gas according to the desired target power generation. This allows the fuel cell to generate electricity. The fuel cell outputs the generated DC power (primary DC power) to the inverter 13.

[0018] The auxiliary equipment 15 is configured to meet the specifications of the first country. Specifically, the rated voltage value of the auxiliary equipment 15 is different from the system voltage value of the power grid 30 of the second country. The auxiliary equipment 15 may also include various devices for operating the power generation unit 10 in addition to the hydrogen gas supply system and the fuel gas supply system.

[0019] The inverter 13 converts the input primary-side DC power into AC power (primary-side AC power) and outputs it to the AC / DC converter 21. The inverter 13 includes an inverter circuit including at least a plurality of switching elements, and converts the primary-side DC power into primary-side AC power by controlling the driving of the switching elements by the control device 40. The inverter 13 may also be configured as a power conditioner including a protection device (not shown) that operates in the event of an abnormality in the power system. The inverter 13 shown in FIG. 1 converts the primary-side DC power into three-phase primary-side AC power and outputs it. However, the primary-side AC power is not limited to three-phase AC power.

[0020] In this embodiment, the inverter 13 is constructed to specifications that satisfy the grid interconnection technical requirements and legal standards of the power grid of a first country, and is unitized with the power generation unit 11. The inverter 13 is configured to specifications that do not satisfy the grid interconnection technical requirements and legal standards of the power grid 30 of a second country to which it is connected. Therefore, the voltage value and frequency of the AC power output from the inverter 13 are different from the system voltage value and frequency of the power grid 30 of the second country. Furthermore, if the inverter 13 is a power conditioner that includes a protection device, the specifications of the protection device are configured to specifications that do not satisfy the grid interconnection technical requirements and legal standards of the power grid 30 of the second country. Therefore, the specifications of the power generation unit 10 do not allow it to be connected to the power grid 30 as is.

[0021] The AC / DC converter 21 converts the input primary-side AC power into DC power (secondary-side DC power) and outputs it to the DC / AC converter 23. In other words, the AC / DC converter 21 has a function of converting the primary-side AC power converted by the inverter 13, which does not satisfy the grid interconnection technical requirements of the power grid 30 of the second country, back into DC power. The AC / DC converter 21 may be, for example, a rectifier circuit having a function of rectifying the primary-side AC power and converting it into DC power, and a function of smoothing the rectified DC power. More specifically, the AC / DC converter 21 may be configured as a capacitor-input rectifier in which a smoothing capacitor is provided in a single-phase diode bridge rectifier circuit having four diodes. The AC / DC converter 21 outputs secondary-side DC power with constant voltage and current values.

[0022] The AC / DC converter 21 may be a converter circuit that includes a plurality of switching elements, and converts primary-side AC power into secondary-side DC power by controlling the driving of the switching elements by the control device 40. However, if the AC / DC converter 21 is the above-mentioned rectifier circuit, it is possible to reduce the processing load on the control device 40 and reduce costs. Furthermore, if the rectifier circuit does not use switching elements, it is possible to suppress a decrease in power efficiency due to the driving of the switching elements.

[0023] The DC / AC converter 23 converts the input secondary-side DC power into AC power (secondary-side AC power) and outputs it to the power grid 30. The DC / AC converter 23 includes an inverter circuit including at least a plurality of switching elements, and converts the secondary-side DC power into secondary-side AC power by controlling the driving of the switching elements by the control device 40. Any DC / AC converter 23 can be suitably used as long as it is configured to specifications that satisfy the grid interconnection technical requirements of the power grid 30 of the second country and is capable of converting DC power into AC power of a desired output voltage and frequency.

[0024] The DC / AC converter 23 may be a power conditioner that converts DC power to AC power and has the functions of adjusting the voltage and stabilizing the frequency. For example, the DC / AC converter 23 may be a power conditioner applied to a solar power generation system used in the second country. With such a DC / AC converter 23, a converter that satisfies the grid interconnection technical requirements and legal standards of the power grid 30 of the second country can be obtained at a relatively low cost. Therefore, the man-hours and costs required for implementation can be reduced.

[0025] Auxiliary DC / AC converter 25 is connected to DC power line 27 connecting AC / DC converter 21 and DC / AC converter 23, and converts the secondary side DC power into auxiliary side AC power of the rated voltage value of auxiliary equipment 15 and outputs it to auxiliary equipment 15. Auxiliary DC / AC converter 25 includes an inverter circuit including at least a plurality of switching elements, and converts the secondary side DC power into single-phase auxiliary side AC power by controlling the driving of the switching elements by control device 40.

[0026] The control device 40 includes at least one arithmetic processing device and a storage element communicatively connected to the arithmetic processing device, and controls the operations of the power generation unit 10, the DC / AC converter 23, and the auxiliary DC / AC converter 25. The control device 40 includes a power generation processing unit 41 and a power conversion processing unit 43. The power generation processing unit 41 and the power conversion processing unit 43 may be functions realized by the execution of a computer program by the arithmetic processing device, or may be configured by analog circuits.

[0027] The power generation processing unit 41 executes control processing of the power generation unit 10 configured to conform to the specifications of the first country. Specifically, the power generation processing unit 41 executes processing to control the operation of the power generation device 11 based on a predetermined target power generation amount and generate power. The control of the operation of the power generation device 11 is a conventionally known control, and detailed description thereof will be omitted. The power generation processing unit 41 also controls the operation of the inverter 13 and executes processing to convert primary side DC power generated by the power generation device 11 into primary side AC power. Specifically, the power generation processing unit 41 executes a processing program designed to conform to the specifications of the first country, thereby converting the primary side DC power into primary side AC power with a system voltage value and frequency of the power grid of the first country.

[0028] The output primary AC power is converted into secondary DC power by AC / DC converter 21 and supplied to DC power line 27 .

[0029] The power conversion processing unit 43 controls the operation of the DC / AC converter 23 and executes a process of converting secondary-side DC power into secondary-side AC power. Specifically, the power conversion processing unit 43 converts the secondary-side DC power into secondary-side AC power having the system voltage value and frequency of the power grid 30 of the second country to which the power grid 30 is connected, and supplies the secondary-side AC power to the power grid 30. The power conversion processing unit 43 also controls the operation of the auxiliary DC / AC converter 25 and executes a process of converting the secondary-side DC power of the DC power line 27 into auxiliary-side AC power. Specifically, the power conversion processing unit 43 converts the secondary-side DC power into auxiliary-side AC power having the rated voltage value and frequency of the auxiliary equipment 15, and supplies the auxiliary equipment 15.

[0030] The power generation processing unit 41 and the power conversion processing unit 43 may be configured as separate control units, or each of the power generation processing unit 41 and the power conversion processing unit 43 may be divided into multiple control units. When the power generation processing unit 41 and the power conversion processing unit 43 are configured as separate control units, a control unit that outputs a command to cooperatively control the multiple control units may be further provided.

[0031] The power generation system 1 configured as described above converts primary AC power output from the power generation unit 10, which has a system voltage and frequency of the power grid of the first country, into secondary DC power using the AC / DC converter 21. The power generation system 1 also converts the secondary DC power into secondary AC power that meets the system voltage and frequency requirements of the power grid 30, using the DC / AC converter 23, which satisfies the grid interconnection technical requirements and legal standards of the connected power grid 30. Therefore, even if the output of the inverter 13 installed in the power generation unit 10 differs from the grid voltage and frequency of the connected power grid 30, the power generation unit 10 can be connected to the power grid 30 while satisfying the grid interconnection technical requirements without using a transformer with a large volume and weight. Furthermore, even if the control of the power generation device 11 and the control of the inverter 13 of the power generation unit 10 are configured in a coordinated manner, the power generation unit 10 can satisfy the grid interconnection technical requirements of the power grid 30 without modifying or replacing the configuration of the power generation unit 10. Therefore, the man-hours and costs required to connect the power generating unit 10 equipped with the inverter 13 that differs from the grid interconnection technical requirements of the connected power grid 30 to the power grid 30 can be reduced.

[0032] Furthermore, since the power generation system 1 has a DC power line 27 connecting the AC / DC converter 21 and the DC / AC converter 23, connecting the auxiliary DC / AC converter 25 to the DC power line 27 makes it possible to supply power to the auxiliary equipment 15 whose rated voltage value differs from the system voltage value of the connected power system 30. Therefore, the power generation unit 10 can be used by connecting to the power system 30 of the second country without modifying or replacing the configuration of the power generation unit 10.

[0033] <Second embodiment> Next, a power generation system according to a second embodiment will be described. The power generation system 1 according to the first embodiment is configured as a system in which one power generation unit 10 is connected to the power grid 30. The power generation system according to the second embodiment is configured as a system in which multiple power generation units are connected to the power grid.

[0034] Fig. 2 is a schematic diagram showing the overall configuration of a power generation system 2 according to a second embodiment. The power generation system 2 is configured with power supply units 3a, 3b, and 3c, each including power generation units 10a, 10b, and 10c and AC / DC converters 21a, 21b, and 21c. Although Fig. 2 shows three power supply units 3a, 3b, and 3c, the number of power supply units may be two, four, or more.

[0035] The auxiliaries 15a, 15b, 15c of the power generation units 10a, 10b, 10c operate by receiving auxiliary-side AC power via an auxiliary DC / AC converter 25 provided in one power supply unit 3c. The AC / DC converters 21a, 21b, 21c of the power supply units 3a, 3b, 3c output secondary-side DC power to a common DC power line 27. A DC / AC converter 23 that converts the secondary-side DC power into secondary-side AC power and outputs it to the power grid 30 is provided as a converter common to all of the power supply units 3a, 3b, 3c.

[0036] The operations of the power generation units 10a, 10b, and 10c, the auxiliary DC / AC converter 25, and the DC / AC converter 23 are controlled by a control device 40. A power generation processing unit 41 and a power conversion processing unit 43 of the control device 40 have the same functions as the respective units of the control device 40 of the power generation system 1 according to the first embodiment. The power generation units 10a, 10b, and 10c are controlled so that the voltage values ​​of the secondary side DC power output from the respective power supply units 3a, 3b, and 3c to the DC power line 27 are the same.

[0037] The control devices for controlling the power generation units 10a, 10b, and 10c may be configured as separate control units. When the control devices for controlling the power generation units 10a, 10b, and 10c are configured as separate control units, a control unit for outputting commands for cooperative control of the plurality of control units may be further provided.

[0038] In the power generation system 2 configured as described above, in each of the power supply units 3a, 3b, 3c, the primary AC power having the system voltage value and frequency of the power system of the first country, output from the power generation units 10a, 10b, 10c, is converted into secondary DC power by an AC / DC converter 21 and output to a common DC power line 27. The output secondary DC power is converted into secondary AC power that satisfies the system voltage value and frequency requirements of the power system 30 by a common DC / AC converter 23 that satisfies the system interconnection technical requirements and legal standards of the connected power system 30, and output to the power system 30. Furthermore, the power generation system 2 according to this embodiment can supply power to each of the auxiliaries 15a, 15b, 15c whose rated voltage value differs from the system voltage value of the connected power system 30, via a common auxiliary DC / AC converter 25 connected to the DC power line 27.

[0039] Therefore, in the power generation system 2 according to this embodiment, in addition to the effects obtained by the power generation system 1 according to the first embodiment, it is possible to reduce the number of DC / AC converters 23, auxiliary DC / AC converters 25, and control devices 40 used relative to the number of power generation units 10a, 10b, 10c. Therefore, it is possible to obtain a greater effect of reducing the man-hours and costs required to connect the power generation units 10a, 10b, 10c equipped with inverters 13 that have different system interconnection technical requirements from the power system 30 to which they are connected to the power system 30.

[0040] <Third embodiment> Next, a power generation system according to a third embodiment will be described. In the power generation systems 1 according to the first and second embodiments, the power generation processing unit 41 executes a processing program designed to meet the specifications of a first country to control the operation of the inverter 13 provided in the power generation unit 10 and converts the primary side DC power into primary side AC power with the system voltage value and frequency of the power grid of the first country. In contrast, the power generation system 1 according to the third embodiment is configured to control the output of the inverter 13 so that the voltage value of the secondary side DC power becomes a voltage value that maximizes the sum of the power conversion efficiency η1 of the inverter 13 and the power conversion efficiency η2 of the DC / AC converter 23.

[0041] Hereinafter, an application example of the power generation system according to this embodiment will be described using the configuration of the power generation system 1 according to the first embodiment as an example. However, the power generation system according to this embodiment can also be similarly applied to the configuration of the power generation system 2 according to the second embodiment.

[0042] Generally, semiconductor power conversion circuits such as inverter circuits have the characteristic that their power conversion efficiency varies because the number of times or the drive duty ratio of switching elements varies depending on the operating conditions. In the power generation system 1, the power conversion efficiency of the inverter 13 provided in the power generation unit 10 varies depending on the magnitude of the output voltage value (voltage value of primary AC power) and the voltage value of the DC power line 27 (voltage value of secondary DC power). Furthermore, the power conversion efficiency of the DC / AC converter 23, which converts secondary DC power into secondary AC power, varies depending on the magnitude of the voltage value of the DC power line 27 (voltage value of secondary DC power), which is the input voltage. In other words, the power conversion efficiencies of both the inverter 13 and the DC / AC converter 23 vary depending on the voltage value of the secondary DC power.

[0043] Therefore, in this embodiment, the control device 40 controls the voltage value of the secondary side DC power so that the sum of the power conversion efficiency η1 of the inverter 13 and the power conversion efficiency η2 of the DC / AC converter 23 is maximized.

[0044] 3 shows an example of the power conversion efficiency η1 of the inverter 13 and the power conversion efficiency η2 of the DC / AC converter 23. When the output voltage value of the power generation device 11 (the voltage value of the primary side DC power) and the output voltage value of the DC / AC converter 23 (the voltage value of the secondary side AC power) are constant, the inverter 13 has a characteristic in which the power conversion efficiency η1 increases as the voltage value of the secondary side DC power V_dc increases, and the power conversion efficiency η1 decreases when the voltage value of the secondary side DC power V_dc exceeds a predetermined value. Furthermore, the DC / AC converter 23 has a characteristic in which the power conversion efficiency η2 increases as the voltage value of the secondary side DC power V_dc increases, and becomes stable when the voltage value of the secondary side DC power V_dc exceeds a predetermined value.

[0045] The power generation processing unit 41 of the control device 40 controls the power generated by the power generation device 11, for example, while maintaining a constant output of the power generation device 11. Since the amount of power generated by the power generation device 11 can fluctuate, the power generation processing unit 41 of the control device 40 sets a target voltage value V_op of the inverter 13 according to the amount of power generated by the power generation device 11 so that the sum of the power conversion efficiency η1 of the inverter 13 and the power conversion efficiency η2 of the DC / AC converter 23 is maximized, and controls the operation of the inverter 13. For example, characteristic data of the power conversion efficiency η1 of the inverter 13 and the power conversion efficiency η2 of the DC / AC converter 23 corresponding to the amount of power generated by the power generation device 11 is stored in advance in a storage element of the control device 40, and the power generation processing unit 41 sets the target voltage value V_op of the inverter 13 according to the amount of power generated by the power generation device 11. When the inverter 13 is an inverter circuit, the power generation processing unit 41 controls the modulation factor so that the voltage value of the primary AC power output from the inverter 13 to the AC / DC converter 21 becomes the target voltage value V_op. Furthermore, the power conversion processing unit 43 controls the operation of the DC / AC converter 23 so that the output voltage value becomes the system voltage value of the power system 30. This reduces power loss caused by driving the switching elements of the inverter 13 and the DC / AC converter 23, and can improve the power conversion efficiency of the power generation system 1.

[0046] In addition, when the AC / DC converter 21 is configured as a converter circuit using switching elements rather than a rectifier using a diode rectifier circuit, the target control amounts of the inverter 13, the AC / DC converter 21, and the DC / AC converter 23 may be set and their respective operations may be controlled so that the sum of the power conversion efficiencies of the inverter 13, the DC / AC converter 23, and the AC / DC converter 21 is maximized.

[0047] In this way, according to the power generation system 1 of this embodiment, it is possible to reduce the labor and cost required to connect a power generation unit 10 equipped with an inverter 13 that has different system interconnection technical requirements from the connected power system 30 to the power system 30, and to increase the power conversion efficiency of the power generation system 1.

[0048] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0049] 1, 2... power generation system, 3a, 3b, 3c... power supply unit, 10, 10a, 10b, 10c... power generation unit, 11, 11a, 11b, 11c... power generation device, 13, 13a, 13b, 13c... inverter, 15, 15a, 15b, 15c... auxiliary equipment, 21, 21a, 21b, 21c... AC / DC converter, 23... DC / AC converter, 25... DC / AC converter for auxiliary equipment, 27... DC power line, 30... power system, 40... control device, 41... power generation processing unit, 43... power conversion processing unit

Claims

1. In a power generation system (1, 2) connected to an electric power system (30), a power generation unit (10) including an inverter (13) that converts primary-side DC power into primary-side AC power and outputs the converted power, the inverter (13) not satisfying the grid interconnection technical requirements of the power grid (30) to which it is connected; an AC / DC converter (21) that converts the primary AC power output from the power generation unit (10) into secondary DC power and outputs the secondary DC power; a DC / AC converter (23) that satisfies the system connection technical requirements of the power system (30) to which it is connected and that converts the secondary DC power output from the AC / DC converter (21) into secondary AC power and outputs the secondary AC power; a control device (40) that controls the power generation system (1), The control device (40) A power generation system that controls the inverter (13) so that the voltage value (V_dc) of the secondary side DC power becomes a voltage value (V_op) that maximizes the sum of at least the power conversion efficiency (η1) of the inverter (13) and the power conversion efficiency (η2) of the DC / AC converter (23).

2. The power generation unit (10) includes a power generation device (11) that outputs the primary side DC power, 2. The power generation system according to claim 1, wherein the power generation device (11) is one of a fuel cell, a solar cell, a wind power generation device, and a hydroelectric power generation device.

3. the power generation unit (10) includes auxiliary machinery (15) that operates on auxiliary-side AC power having a rated voltage different from the system voltage value of the power system (30) to which the power generation unit (10) is connected; 3. The power generation system according to claim 1, further comprising: an auxiliary DC / AC converter (25) connected to a DC power line (27) connecting the AC / DC converter (21) and the DC / AC converter (23), converting a voltage value of the secondary side DC power to a rated voltage of the auxiliary equipment (15) and supplying the auxiliary side AC power to the auxiliary equipment (15).

4. The power generation system (2) A plurality of the power generation units (10a, 10b, 10c); a plurality of AC / DC converters (21a, 21b, 21c) connected to the plurality of power generating units (10a, 10b, 10c), respectively; one DC / AC converter (23) connected to the plurality of AC / DC converters (21a, 21b, 21c); the control device (40) that controls the power generation system (2); The power generation system according to any one of claims 1 to 3, comprising:

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